Cheek heading excavation with consolidation and reinforcement of the ground properties

• Tunnel within ground water table and/or lose ground
• Dense to very dense sand layers
• In the excavation direction a saturated water ground of at least 1m was expected
• Strong water inrush from the upper vault exploration holes

After about 165m of driving, water and sand from the ridge of the calotte of the U9 elm adit (north) penetrated during an exploratory drilling. The stratigraphic section shows that about 1 m above the ridge there is a water dam about 1 m thick, which dips flat into the tunnel profile in the direction of driving. Above it there is fine saturated fine sand.